Diphenylethylamine derivatives were well recognized analgesic ( Japanese Patent Publication 24084/1961 etc.) and especially (-)-N,N-dimethyl-1,2-diphenylethylamine, lefetamine, is known to have an excellent analgesic effect.
Chemical modification of amine moiety was also studied, and diphenylethylpiperazine derivatives were reported in Japanese Patent Publication 33827/1986 to have an analgesic effect. Furthermore, we reported that diphenylethylpiperazine derivatives had a calcium antagonistic effect Japanese Unexamined Patent Publication 141966/1988 ). Diphenylethylpiperazine derivatives were already known to have analgesic effect and calcium antagonistic effect, but the other useful pharmacological properties were not known.